Life Under the Ice
The Subnivium
A couple of months ago, the entire county of Pocahontas was clad in ice up to eight inches thick. Pocahontas Times staff writer Lucas Adcock wrote an interesting story discussing the effects and extent of the unprecedented ice storm we experienced in January.
This, however, is a story about what was going on under the ice that few know about. While life for livestock, deer and humans was tough on top of the ice sheet, all the while there was a party going on under the ice.
If you have previously never heard about an ecosystem called the subnivium, you’re not alone: I imagined that if life was challenging on top of the ice, then it must be even colder and more hostile beneath the ice – but I was wrong. It would take a week or so before I stumbled onto something that led me to the concept of a subnivium biome.
Every morning, I run on trails in a woodlot just a few yards from my back door. This small forest is composed of huge white pines, mixed hardwoods, and rhododendron. A large vernal pool borders the northern boundary of the woods.
The trails weave around the largest trees, passing by the pool. I know from two years of building and running those trails that this small woodlot is home to several species of amphibians, including frogs and salamanders.
Underneath the pine needles and decaying leaves, a wide variety of arthropods roam, including centipedes, millipedes, beetles, and spiders. Meanwhile, on top of the forest duff, we find chipmunks, squirrels, rabbits and the occasional weasel or fox.
As you know, the armor of ice here in Pocahontas County was solid blue ice,* strong enough to bear the weight of humans and vehicles. Near the end of the first week, six to eight inches of hard ice covered the forest floor, and it was then that I noticed three perfectly circular holes in the ice that seemed to appear overnight. These holes couldn’t have been more uniform in size if they were cut with a hole saw.
Just outside the three-inch holes were pine needles and bits of forest duff. At first, I assumed the holes, however perfect, were made by a squirrel searching for hidden nuts. But, in the following days, as more holes began appearing each succeeding morning, I noticed some chipmunk tracks coming out of the hole and entering nearby holes. “What in the world is going on down there?” I thought.
It didn’t take much online research before the word “Subnivium” came up, along with some diagrams depicting a whole ecosystem alive and thriving during the iced-over period.
The subnivium creatures that thrive under heavy ice or snowpack vary depending on which part of the world they live in. While chipmunks, voles and moles are what we would find under the ice here in West Virginia, one would find martens, ermine, pikas, marmots and lemmings in other locations in higher latitudes and elevations.
Even grouse will utilize the insulation and warmth of snowpack by forcefully diving into the snow for shelter during the night. In a sense, the subnivium is nature’s own igloo for critters.
Unknown to me at the time was the temperature gradient between the ice surface and that just below the thick cold blanket. It seems counterintuitive, but regardless of the ambient temperature above, the temperature below is always 1.8 degrees Fahrenheit above freezing.
This consistently above-freezing environment allows the various lifeforms to continue mating, feeding and hunting. Small mammals, such as chipmunks, rise from their winter state of torpor every few days to hunt for food. To do so, they move about under the ice, creating a maze of under-ice passages and holes to access the surface.
(This is why you may have noticed a few holes one day, only to come back and find many more the next day, as I did.)
Down there, scurrying about in the subnivium, are three species of predatory Rove Beetles that eat nuisance insects that threaten forest plants and trees. Throughout the forest floor, there is all manner of microbial life.
Microbial and fungal activity of breaking down the leaf matter is essential for the health of all plant life in the forest, and, therefore, important to the mammals and birds as well. In the case of microbes and fungi, they breathe in oxygen and respire carbon, which further enriches the forest floor.
With global warming posing a direct threat to forests and everything in them, the time will come when the inevitable loss of snowpack leaves unprotected microbes vulnerable to freezing. When this happens, the decaying microbes will release their carbon too early in the season, preventing normal plant growth.
Clearly, the subnivium ecosystem is finely balanced and has developed over millennia. This fact makes it vulnerable to rising temperatures worldwide.
The same can be said of vernal pools, another unique form of nature’s ecosystems. These intermittent bodies of water are essential for maintaining amphibian life. Vernal pools mysteriously produce water during the mating season of frogs and salamanders. Once the amphibians lay their eggs and the larval stage matures, the tadpoles go from an aquatic to a terrestrial life, and the pool promptly dries up; hence, fish cannot exist, as they would eat all the tadpoles.
Global warming threatens so much of what we recognize as natural systems that support the lives of many types of creatures. Several times in Earth’s history, climate change has wiped the slate clean of most or all life, and new life forms have emerged. But what many do not believe, or ignore, is that the list of endangered species in this next global catastrophe could very well include Homo sapiens.
Right now, the world seems horribly divided, and division erodes cooperation. What a thinking world would do is address the problems now rather than selfishly leave these existential threats for our children and future generations to deal with.
If we really care about this planet, we should take a break from unnecessary wars and fight the war that is now raging in nature before it’s too late.
Ken Springer
ken1949bongo@gmail.com
*Blue ice contains fewer air bubbles than other naturally occurring ice forms. Therefore, it is stronger and highly sought after by ice climbers.
An alternative spelling of subnivium is subnivean.
